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1da177e4 LT |
1 | |
2 | #include <linux/fs.h> | |
3 | #include <linux/file.h> | |
4 | #include <linux/module.h> | |
5 | #include <linux/smp_lock.h> | |
6 | #include <linux/namei.h> | |
7 | ||
8 | struct export_operations export_op_default; | |
9 | ||
10 | #define CALL(ops,fun) ((ops->fun)?(ops->fun):export_op_default.fun) | |
11 | ||
12 | #define dprintk(fmt, args...) do{}while(0) | |
13 | ||
14 | /** | |
15 | * find_exported_dentry - helper routine to implement export_operations->decode_fh | |
16 | * @sb: The &super_block identifying the filesystem | |
17 | * @obj: An opaque identifier of the object to be found - passed to | |
18 | * get_inode | |
19 | * @parent: An optional opqaue identifier of the parent of the object. | |
20 | * @acceptable: A function used to test possible &dentries to see if they are | |
21 | * acceptable | |
22 | * @context: A parameter to @acceptable so that it knows on what basis to | |
23 | * judge. | |
24 | * | |
25 | * find_exported_dentry is the central helper routine to enable file systems | |
26 | * to provide the decode_fh() export_operation. It's main task is to take | |
27 | * an &inode, find or create an appropriate &dentry structure, and possibly | |
28 | * splice this into the dcache in the correct place. | |
29 | * | |
30 | * The decode_fh() operation provided by the filesystem should call | |
31 | * find_exported_dentry() with the same parameters that it received except | |
32 | * that instead of the file handle fragment, pointers to opaque identifiers | |
33 | * for the object and optionally its parent are passed. The default decode_fh | |
34 | * routine passes one pointer to the start of the filehandle fragment, and | |
35 | * one 8 bytes into the fragment. It is expected that most filesystems will | |
36 | * take this approach, though the offset to the parent identifier may well be | |
37 | * different. | |
38 | * | |
39 | * find_exported_dentry() will call get_dentry to get an dentry pointer from | |
40 | * the file system. If any &dentry in the d_alias list is acceptable, it will | |
41 | * be returned. Otherwise find_exported_dentry() will attempt to splice a new | |
42 | * &dentry into the dcache using get_name() and get_parent() to find the | |
43 | * appropriate place. | |
44 | */ | |
45 | ||
46 | struct dentry * | |
47 | find_exported_dentry(struct super_block *sb, void *obj, void *parent, | |
48 | int (*acceptable)(void *context, struct dentry *de), | |
49 | void *context) | |
50 | { | |
51 | struct dentry *result = NULL; | |
52 | struct dentry *target_dir; | |
53 | int err; | |
54 | struct export_operations *nops = sb->s_export_op; | |
55 | struct list_head *le, *head; | |
56 | struct dentry *toput = NULL; | |
57 | int noprogress; | |
58 | char nbuf[NAME_MAX+1]; | |
59 | ||
60 | /* | |
61 | * Attempt to find the inode. | |
62 | */ | |
63 | result = CALL(sb->s_export_op,get_dentry)(sb,obj); | |
64 | err = -ESTALE; | |
65 | if (result == NULL) | |
66 | goto err_out; | |
67 | if (IS_ERR(result)) { | |
68 | err = PTR_ERR(result); | |
69 | goto err_out; | |
70 | } | |
71 | if (S_ISDIR(result->d_inode->i_mode) && | |
72 | (result->d_flags & DCACHE_DISCONNECTED)) { | |
73 | /* it is an unconnected directory, we must connect it */ | |
74 | ; | |
75 | } else { | |
76 | if (acceptable(context, result)) | |
77 | return result; | |
78 | if (S_ISDIR(result->d_inode->i_mode)) { | |
79 | /* there is no other dentry, so fail */ | |
80 | goto err_result; | |
81 | } | |
82 | /* try any other aliases */ | |
83 | spin_lock(&dcache_lock); | |
84 | head = &result->d_inode->i_dentry; | |
85 | list_for_each(le, head) { | |
86 | struct dentry *dentry = list_entry(le, struct dentry, d_alias); | |
87 | dget_locked(dentry); | |
88 | spin_unlock(&dcache_lock); | |
89 | if (toput) | |
90 | dput(toput); | |
91 | toput = NULL; | |
92 | if (dentry != result && | |
93 | acceptable(context, dentry)) { | |
94 | dput(result); | |
95 | return dentry; | |
96 | } | |
97 | spin_lock(&dcache_lock); | |
98 | toput = dentry; | |
99 | } | |
100 | spin_unlock(&dcache_lock); | |
101 | if (toput) | |
102 | dput(toput); | |
103 | } | |
104 | ||
105 | /* It's a directory, or we are required to confirm the file's | |
106 | * location in the tree based on the parent information | |
107 | */ | |
108 | dprintk("find_exported_dentry: need to look harder for %s/%d\n",sb->s_id,*(int*)obj); | |
109 | if (S_ISDIR(result->d_inode->i_mode)) | |
110 | target_dir = dget(result); | |
111 | else { | |
112 | if (parent == NULL) | |
113 | goto err_result; | |
114 | ||
115 | target_dir = CALL(sb->s_export_op,get_dentry)(sb,parent); | |
116 | if (IS_ERR(target_dir)) | |
117 | err = PTR_ERR(target_dir); | |
118 | if (target_dir == NULL || IS_ERR(target_dir)) | |
119 | goto err_result; | |
120 | } | |
121 | /* | |
122 | * Now we need to make sure that target_dir is properly connected. | |
123 | * It may already be, as the flag isn't always updated when connection | |
124 | * happens. | |
125 | * So, we walk up parent links until we find a connected directory, | |
126 | * or we run out of directories. Then we find the parent, find | |
127 | * the name of the child in that parent, and do a lookup. | |
128 | * This should connect the child into the parent | |
129 | * We then repeat. | |
130 | */ | |
131 | ||
132 | /* it is possible that a confused file system might not let us complete | |
133 | * the path to the root. For example, if get_parent returns a directory | |
134 | * in which we cannot find a name for the child. While this implies a | |
135 | * very sick filesystem we don't want it to cause knfsd to spin. Hence | |
136 | * the noprogress counter. If we go through the loop 10 times (2 is | |
137 | * probably enough) without getting anywhere, we just give up | |
138 | */ | |
139 | noprogress= 0; | |
140 | while (target_dir->d_flags & DCACHE_DISCONNECTED && noprogress++ < 10) { | |
141 | struct dentry *pd = target_dir; | |
142 | ||
143 | dget(pd); | |
144 | spin_lock(&pd->d_lock); | |
145 | while (!IS_ROOT(pd) && | |
146 | (pd->d_parent->d_flags&DCACHE_DISCONNECTED)) { | |
147 | struct dentry *parent = pd->d_parent; | |
148 | ||
149 | dget(parent); | |
150 | spin_unlock(&pd->d_lock); | |
151 | dput(pd); | |
152 | pd = parent; | |
153 | spin_lock(&pd->d_lock); | |
154 | } | |
155 | spin_unlock(&pd->d_lock); | |
156 | ||
157 | if (!IS_ROOT(pd)) { | |
158 | /* must have found a connected parent - great */ | |
159 | spin_lock(&pd->d_lock); | |
160 | pd->d_flags &= ~DCACHE_DISCONNECTED; | |
161 | spin_unlock(&pd->d_lock); | |
162 | noprogress = 0; | |
163 | } else if (pd == sb->s_root) { | |
164 | printk(KERN_ERR "export: Eeek filesystem root is not connected, impossible\n"); | |
165 | spin_lock(&pd->d_lock); | |
166 | pd->d_flags &= ~DCACHE_DISCONNECTED; | |
167 | spin_unlock(&pd->d_lock); | |
168 | noprogress = 0; | |
169 | } else { | |
170 | /* we have hit the top of a disconnected path. Try | |
171 | * to find parent and connect | |
172 | * note: racing with some other process renaming a | |
173 | * directory isn't much of a problem here. If someone | |
174 | * renames the directory, it will end up properly | |
175 | * connected, which is what we want | |
176 | */ | |
177 | struct dentry *ppd; | |
178 | struct dentry *npd; | |
179 | ||
180 | down(&pd->d_inode->i_sem); | |
181 | ppd = CALL(nops,get_parent)(pd); | |
182 | up(&pd->d_inode->i_sem); | |
183 | ||
184 | if (IS_ERR(ppd)) { | |
185 | err = PTR_ERR(ppd); | |
186 | dprintk("find_exported_dentry: get_parent of %ld failed, err %d\n", | |
187 | pd->d_inode->i_ino, err); | |
188 | dput(pd); | |
189 | break; | |
190 | } | |
191 | dprintk("find_exported_dentry: find name of %lu in %lu\n", pd->d_inode->i_ino, ppd->d_inode->i_ino); | |
192 | err = CALL(nops,get_name)(ppd, nbuf, pd); | |
193 | if (err) { | |
194 | dput(ppd); | |
195 | dput(pd); | |
196 | if (err == -ENOENT) | |
197 | /* some race between get_parent and | |
198 | * get_name? just try again | |
199 | */ | |
200 | continue; | |
201 | break; | |
202 | } | |
203 | dprintk("find_exported_dentry: found name: %s\n", nbuf); | |
204 | down(&ppd->d_inode->i_sem); | |
205 | npd = lookup_one_len(nbuf, ppd, strlen(nbuf)); | |
206 | up(&ppd->d_inode->i_sem); | |
207 | if (IS_ERR(npd)) { | |
208 | err = PTR_ERR(npd); | |
209 | dprintk("find_exported_dentry: lookup failed: %d\n", err); | |
210 | dput(ppd); | |
211 | dput(pd); | |
212 | break; | |
213 | } | |
214 | /* we didn't really want npd, we really wanted | |
215 | * a side-effect of the lookup. | |
216 | * hopefully, npd == pd, though it isn't really | |
217 | * a problem if it isn't | |
218 | */ | |
219 | if (npd == pd) | |
220 | noprogress = 0; | |
221 | else | |
222 | printk("find_exported_dentry: npd != pd\n"); | |
223 | dput(npd); | |
224 | dput(ppd); | |
225 | if (IS_ROOT(pd)) { | |
226 | /* something went wrong, we have to give up */ | |
227 | dput(pd); | |
228 | break; | |
229 | } | |
230 | } | |
231 | dput(pd); | |
232 | } | |
233 | ||
234 | if (target_dir->d_flags & DCACHE_DISCONNECTED) { | |
235 | /* something went wrong - oh-well */ | |
236 | if (!err) | |
237 | err = -ESTALE; | |
238 | goto err_target; | |
239 | } | |
240 | /* if we weren't after a directory, have one more step to go */ | |
241 | if (result != target_dir) { | |
242 | struct dentry *nresult; | |
243 | err = CALL(nops,get_name)(target_dir, nbuf, result); | |
244 | if (!err) { | |
245 | down(&target_dir->d_inode->i_sem); | |
246 | nresult = lookup_one_len(nbuf, target_dir, strlen(nbuf)); | |
247 | up(&target_dir->d_inode->i_sem); | |
248 | if (!IS_ERR(nresult)) { | |
249 | if (nresult->d_inode) { | |
250 | dput(result); | |
251 | result = nresult; | |
252 | } else | |
253 | dput(nresult); | |
254 | } | |
255 | } | |
256 | } | |
257 | dput(target_dir); | |
258 | /* now result is properly connected, it is our best bet */ | |
259 | if (acceptable(context, result)) | |
260 | return result; | |
261 | /* one last try of the aliases.. */ | |
262 | spin_lock(&dcache_lock); | |
263 | toput = NULL; | |
264 | head = &result->d_inode->i_dentry; | |
265 | list_for_each(le, head) { | |
266 | struct dentry *dentry = list_entry(le, struct dentry, d_alias); | |
267 | dget_locked(dentry); | |
268 | spin_unlock(&dcache_lock); | |
269 | if (toput) dput(toput); | |
270 | if (dentry != result && | |
271 | acceptable(context, dentry)) { | |
272 | dput(result); | |
273 | return dentry; | |
274 | } | |
275 | spin_lock(&dcache_lock); | |
276 | toput = dentry; | |
277 | } | |
278 | spin_unlock(&dcache_lock); | |
279 | if (toput) | |
280 | dput(toput); | |
281 | ||
282 | /* drat - I just cannot find anything acceptable */ | |
283 | dput(result); | |
284 | /* It might be justifiable to return ESTALE here, | |
285 | * but the filehandle at-least looks reasonable good | |
286 | * and it just be a permission problem, so returning | |
287 | * -EACCESS is safer | |
288 | */ | |
289 | return ERR_PTR(-EACCES); | |
290 | ||
291 | err_target: | |
292 | dput(target_dir); | |
293 | err_result: | |
294 | dput(result); | |
295 | err_out: | |
296 | return ERR_PTR(err); | |
297 | } | |
298 | ||
299 | ||
300 | ||
301 | static struct dentry *get_parent(struct dentry *child) | |
302 | { | |
303 | /* get_parent cannot be supported generically, the locking | |
304 | * is too icky. | |
305 | * instead, we just return EACCES. If server reboots or inodes | |
306 | * get flushed, you lose | |
307 | */ | |
308 | return ERR_PTR(-EACCES); | |
309 | } | |
310 | ||
311 | ||
312 | struct getdents_callback { | |
313 | char *name; /* name that was found. It already points to a | |
314 | buffer NAME_MAX+1 is size */ | |
315 | unsigned long ino; /* the inum we are looking for */ | |
316 | int found; /* inode matched? */ | |
317 | int sequence; /* sequence counter */ | |
318 | }; | |
319 | ||
320 | /* | |
321 | * A rather strange filldir function to capture | |
322 | * the name matching the specified inode number. | |
323 | */ | |
324 | static int filldir_one(void * __buf, const char * name, int len, | |
325 | loff_t pos, ino_t ino, unsigned int d_type) | |
326 | { | |
327 | struct getdents_callback *buf = __buf; | |
328 | int result = 0; | |
329 | ||
330 | buf->sequence++; | |
331 | if (buf->ino == ino) { | |
332 | memcpy(buf->name, name, len); | |
333 | buf->name[len] = '\0'; | |
334 | buf->found = 1; | |
335 | result = -1; | |
336 | } | |
337 | return result; | |
338 | } | |
339 | ||
340 | /** | |
341 | * get_name - default export_operations->get_name function | |
342 | * @dentry: the directory in which to find a name | |
343 | * @name: a pointer to a %NAME_MAX+1 char buffer to store the name | |
344 | * @child: the dentry for the child directory. | |
345 | * | |
346 | * calls readdir on the parent until it finds an entry with | |
347 | * the same inode number as the child, and returns that. | |
348 | */ | |
349 | static int get_name(struct dentry *dentry, char *name, | |
350 | struct dentry *child) | |
351 | { | |
352 | struct inode *dir = dentry->d_inode; | |
353 | int error; | |
354 | struct file *file; | |
355 | struct getdents_callback buffer; | |
356 | ||
357 | error = -ENOTDIR; | |
358 | if (!dir || !S_ISDIR(dir->i_mode)) | |
359 | goto out; | |
360 | error = -EINVAL; | |
361 | if (!dir->i_fop) | |
362 | goto out; | |
363 | /* | |
364 | * Open the directory ... | |
365 | */ | |
366 | file = dentry_open(dget(dentry), NULL, O_RDONLY); | |
367 | error = PTR_ERR(file); | |
368 | if (IS_ERR(file)) | |
369 | goto out; | |
370 | ||
371 | error = -EINVAL; | |
372 | if (!file->f_op->readdir) | |
373 | goto out_close; | |
374 | ||
375 | buffer.name = name; | |
376 | buffer.ino = child->d_inode->i_ino; | |
377 | buffer.found = 0; | |
378 | buffer.sequence = 0; | |
379 | while (1) { | |
380 | int old_seq = buffer.sequence; | |
381 | ||
382 | error = vfs_readdir(file, filldir_one, &buffer); | |
383 | ||
384 | if (error < 0) | |
385 | break; | |
386 | ||
387 | error = 0; | |
388 | if (buffer.found) | |
389 | break; | |
390 | error = -ENOENT; | |
391 | if (old_seq == buffer.sequence) | |
392 | break; | |
393 | } | |
394 | ||
395 | out_close: | |
396 | fput(file); | |
397 | out: | |
398 | return error; | |
399 | } | |
400 | ||
401 | ||
402 | static struct dentry *export_iget(struct super_block *sb, unsigned long ino, __u32 generation) | |
403 | { | |
404 | ||
405 | /* iget isn't really right if the inode is currently unallocated!! | |
406 | * This should really all be done inside each filesystem | |
407 | * | |
408 | * ext2fs' read_inode has been strengthed to return a bad_inode if | |
409 | * the inode had been deleted. | |
410 | * | |
411 | * Currently we don't know the generation for parent directory, so | |
412 | * a generation of 0 means "accept any" | |
413 | */ | |
414 | struct inode *inode; | |
415 | struct dentry *result; | |
416 | if (ino == 0) | |
417 | return ERR_PTR(-ESTALE); | |
418 | inode = iget(sb, ino); | |
419 | if (inode == NULL) | |
420 | return ERR_PTR(-ENOMEM); | |
421 | if (is_bad_inode(inode) | |
422 | || (generation && inode->i_generation != generation) | |
423 | ) { | |
424 | /* we didn't find the right inode.. */ | |
425 | dprintk("fh_verify: Inode %lu, Bad count: %d %d or version %u %u\n", | |
426 | inode->i_ino, | |
427 | inode->i_nlink, atomic_read(&inode->i_count), | |
428 | inode->i_generation, | |
429 | generation); | |
430 | ||
431 | iput(inode); | |
432 | return ERR_PTR(-ESTALE); | |
433 | } | |
434 | /* now to find a dentry. | |
435 | * If possible, get a well-connected one | |
436 | */ | |
437 | result = d_alloc_anon(inode); | |
438 | if (!result) { | |
439 | iput(inode); | |
440 | return ERR_PTR(-ENOMEM); | |
441 | } | |
442 | return result; | |
443 | } | |
444 | ||
445 | ||
446 | static struct dentry *get_object(struct super_block *sb, void *vobjp) | |
447 | { | |
448 | __u32 *objp = vobjp; | |
449 | unsigned long ino = objp[0]; | |
450 | __u32 generation = objp[1]; | |
451 | ||
452 | return export_iget(sb, ino, generation); | |
453 | } | |
454 | ||
455 | ||
456 | /** | |
457 | * export_encode_fh - default export_operations->encode_fh function | |
458 | * @dentry: the dentry to encode | |
459 | * @fh: where to store the file handle fragment | |
460 | * @max_len: maximum length to store there | |
461 | * @connectable: whether to store parent information | |
462 | * | |
463 | * This default encode_fh function assumes that the 32 inode number | |
464 | * is suitable for locating an inode, and that the generation number | |
465 | * can be used to check that it is still valid. It places them in the | |
466 | * filehandle fragment where export_decode_fh expects to find them. | |
467 | */ | |
468 | static int export_encode_fh(struct dentry *dentry, __u32 *fh, int *max_len, | |
469 | int connectable) | |
470 | { | |
471 | struct inode * inode = dentry->d_inode; | |
472 | int len = *max_len; | |
473 | int type = 1; | |
474 | ||
475 | if (len < 2 || (connectable && len < 4)) | |
476 | return 255; | |
477 | ||
478 | len = 2; | |
479 | fh[0] = inode->i_ino; | |
480 | fh[1] = inode->i_generation; | |
481 | if (connectable && !S_ISDIR(inode->i_mode)) { | |
482 | struct inode *parent; | |
483 | ||
484 | spin_lock(&dentry->d_lock); | |
485 | parent = dentry->d_parent->d_inode; | |
486 | fh[2] = parent->i_ino; | |
487 | fh[3] = parent->i_generation; | |
488 | spin_unlock(&dentry->d_lock); | |
489 | len = 4; | |
490 | type = 2; | |
491 | } | |
492 | *max_len = len; | |
493 | return type; | |
494 | } | |
495 | ||
496 | ||
497 | /** | |
498 | * export_decode_fh - default export_operations->decode_fh function | |
499 | * @sb: The superblock | |
500 | * @fh: pointer to the file handle fragment | |
501 | * @fh_len: length of file handle fragment | |
502 | * @acceptable: function for testing acceptability of dentrys | |
503 | * @context: context for @acceptable | |
504 | * | |
505 | * This is the default decode_fh() function. | |
506 | * a fileid_type of 1 indicates that the filehandlefragment | |
507 | * just contains an object identifier understood by get_dentry. | |
508 | * a fileid_type of 2 says that there is also a directory | |
509 | * identifier 8 bytes in to the filehandlefragement. | |
510 | */ | |
511 | static struct dentry *export_decode_fh(struct super_block *sb, __u32 *fh, int fh_len, | |
512 | int fileid_type, | |
513 | int (*acceptable)(void *context, struct dentry *de), | |
514 | void *context) | |
515 | { | |
516 | __u32 parent[2]; | |
517 | parent[0] = parent[1] = 0; | |
518 | if (fh_len < 2 || fileid_type > 2) | |
519 | return NULL; | |
520 | if (fileid_type == 2) { | |
521 | if (fh_len > 2) parent[0] = fh[2]; | |
522 | if (fh_len > 3) parent[1] = fh[3]; | |
523 | } | |
524 | return find_exported_dentry(sb, fh, parent, | |
525 | acceptable, context); | |
526 | } | |
527 | ||
528 | struct export_operations export_op_default = { | |
529 | .decode_fh = export_decode_fh, | |
530 | .encode_fh = export_encode_fh, | |
531 | ||
532 | .get_name = get_name, | |
533 | .get_parent = get_parent, | |
534 | .get_dentry = get_object, | |
535 | }; | |
536 | ||
537 | EXPORT_SYMBOL(export_op_default); | |
538 | EXPORT_SYMBOL(find_exported_dentry); | |
539 | ||
540 | MODULE_LICENSE("GPL"); |